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Ram Prasad Gandhiraman | Company: Space Foundry Inc SAVE THE DATE

Speaker: Georg Boedler Company: Inkatronic Inkatronic has over 25 years’ experience in inkjet technologies, and develops specialised industrial machines for mass production. Implementing an inkjet solution to industrial processes can create incredible advantages, as well as open up new opportunities for manufacturing. However, scaling up a solution from a proven laboratory method to a mass-manufacturing environment is surprisingly difficult. In our presentation, we will give a breakdown of some of the challenges that need to be overcome in order to achieve this successfully. SAVE THE DATE

Micro electronic pattern and flat cable core manufacturing process with electroforming by roll to roll equipments. This process can be applied to the development of flexible flat-cable, copper electrode of solar cell and flexible electonic components. The first advantage of this process is that relative long and wide scale metal pattern could be produced. SAVE THE DATE

By Mikael Boedler, INKATRONIC GmbH | mb@inkatronic.com Niederdorfstrasse 6, 4063 Hörsching Tel.: +43 7221 22298 In this article, we will discuss the different aspects of an effective ink delivery system. We will focus on a recirculating inkjet system as they are highly in demand in industry, especially where functional fluids come into play. Though recirculating printheads are mostly on the same price level as non-recirculating, gravity feed equivalents the ink supply system needed is much more intricate and as a result, significantly more challenging to implement (an example of a recirculating ink delivery system is shown in figure 1 below). The benefits of recirculating systems, however, are clearly outlined in the next section making it a worthy endeavour. Figure 1 - INKATRONIC Scalable Circulating Ink Supply. Advantages of Recirculating Inkjet Technology in Industry Improved Print Quality - Recirculating printheads maintain a consistent ink temperature and viscosity, resulting in more consistent droplet formation when jetting at various frequencies. This leads to a better print quality with sharper details and better lay-down accuracy. Reduced Nozzle failures - Continuous ink circulation helps prevent nozzle failures caused by ingesting air, ink drying out, or ink settling, ensuring uninterrupted printing. Faster Start-Up Times - most recirculating printheads can start printing immediately, whereas gravity-feed printheads may require cleaning cycles to recover missing nozzles. Enhanced Printhead Longevity - The reduced risk of nozzle clogs and more stable operating conditions can extend the lifespan of recirculating printheads when compared to gravity feed systems. Improved Jetting Consistency - The stability in ink properties provided by recirculating printheads helps maintain consistent output across multiple print jobs, making them suitable for high-volume and continuous printing applications. Reduced Maintenance - Gravity feed printheads may require more frequent cleaning, purging, and maintenance, while recirculating printheads need less attention, leading to lower downtime and operating costs. Join us at TechBlick's Future of Electronics RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped. For your special attendee discounts please contact us. Basic Principles of a Recirculating Ink Delivery System In theory, a recirculating ink supply is simple. By creating a pressure difference between the “in” and “out” ports of a printhead a flow of ink is generated (see Figure 2). At the same time, the correct pressure difference must be maintained to generate a slightly negative meniscus pressure at the nozzles. Achieving such a state initially is relatively easy, the hard part is maintaining it while the printhead starts jetting, recirculating pumps run and ink is refilled to compensate for the rate of ink leaving the system. Figure 2 - A simple diagram showing two ink tanks with different pressures connected to a printhead. Pin is higher than Pout causing ink flow through the printhead. The overall pressure at the printhead will determine if a meniscus is held at the printhead nozzles. Figure 3 - INKATRONIC Single Head Circulating Ink Supply. What are the Requirements for a Recirculating Ink Delivery System Pressure Control A meniscus pressure operating window is around ±2 mbar. Though changes within this range are unlikely to affect jetting stability, drop properties will always be affected by the smallest changes causing shifts in printed densities. For this reason, keeping the meniscus pressure within an optimal range is essential. Ink Pumps A reliable ink pump is essential for circulating ink through the system. Diaphragm pumps are commonly used for inkjet applications due to their accuracy and low maintenance requirements, though they must offer good speed control. Sharp start/stop operations are undesired and low pulsation is essential. Peristaltic pumps have their advantages but they need more frequent maintenance with their tubes, while gear pumps should be avoided due to their high shear rates which can affect an ink’s properties in circulating loops. For good chemical resistance, in the case of diaphragm pumps, they should contain FFKM valves and seals. Teflon is the recommended material for membranes. Join us at TechBlick's Future of Electronics RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped. For your special attendee discounts please contact us at mb@inkatronic.com. Valves As a general rule, valves should be avoided where possible. If needed they have to be compact, with FFKM elastomers, large orifices, and low power consumption. This combination is often not available as standard and a partnership with a manufacturer is required to develop such valves. Pressure Spikes Pumps and valves create varying pulses of pressure, each of them, or in combination, can lead to undesired spikes in pressure. Pressure spikes can cause an immediate loss of nozzles. A positive spike can float a nozzle causing nozzle plate wetting (as shown in figure 3) and a cleaning stop. A negative pressure spike can lead to nozzle drop-outs by the ingestion of air (as shown in figure 4). In the case of a momentary ingestion of air, this is less consequential as the circulating flow of ink will quickly recover the nozzles. An acceptable range for pressure spikes can be +5 to -10 mbar, noting that the “in” pressure is most sensitive to this. It should also be noted that in some cases when large amounts of nozzles are started/stopped simultaneously they themselves can cause pressure spikes at the inlet side of the printhead. Figure 4 - Shows a printhead nozzle plate wetting. This is due to a positive pressure at the nozzle plate. Figure 5 - Shows a printhead nozzle ingesting air. This is due to too high negative pressure at the nozzle plate. Tubing and Connectors Appropriate fittings and tubing should be used that are compatible with the inks chosen for the printing application. Long-term testing should be conducted to observe shrinking, swelling, and sweating. All tubes should be kept as short as possible and with multiple heads they have to be exactly equal in the length. High-quality connectors are recommended as a leaking inkjet system can cause lots of trouble to fix, not to mention the mess. More critical though, is the ingestion of air at any point of the negative pressure side of the system, such a leak is almost impossible to identify. This causes Ink foaming which provokes large jetting dropouts and the level control system to give false readings, which can cause an ink overflow. Materials for Manifolds and Tanks The material chosen for an ink tank should be compatible with the ink chemistry, preventing any chemical reactions or contamination. Common materials for ink tanks are stainless steel, high-density polyethylene (HDPE), polypropylene (PP) and aluminium. In the case of aluminium, it should never be used with water-based inks. Sedimentation and Draining of the system Sedimentation can occur in only a few hours which leads to unstable jetting and nozzle clogging. To avoid sedimentation of high-density inks they need constant motion or stirring. Ink should be kept circulating through the entire ink supply system and extended idle times should be avoided. For a weekend shutdown, it is recommended to implement an automatic draining process to remove the ink from the system and keep it agitated in the main ink reservoir. Temperature Control Ink temperature should be maintained precisely at the optimal value, deviating only ±1°C. This has to be controlled at the tanks and at each printhead. The tank heaters have to be well distributed, local overheating of ink must be avoided. Flow-through heaters in the ink recirculation lines can be used in addition, if needed. Experiments have to be conducted in order to determine an ink’s sensitivity to temperature. Printheads with integrated heaters should reach the target ink temperature with the heater switched off, otherwise the temperature reading by the head thermistor may not be representative of the ink temperature at the “in” and “out” ports. Printhead heaters should be used for fine-tuning the ink temperature, raising it by not more than 2°C. Degassing, Air Bubble Removal Ink formulations can contain dissolved gases or air bubbles, which can disrupt the flow of a fluid within the printhead. A degasser removes these entrapped gases from the ink, resulting in more stable and reliable jetting. This is especially recommended for water-based inks, while UV and solvent-based inks will always show improvements from this. The Parameters for Setting up an Inkjet System For each specific ink and printhead, a different set of parameters will need to be determined. These parameters include: Temperature. “In” and “out” pressures. Flow rate. Head voltage. Waveform. These parameters must be determined experimentally by setting up an ink supply system, with a chosen printhead, the printhead electronics and the ink of choice. When testing a new ink the starting point should be to set the recommended temperature/viscosity set-points provided by the ink manufacturer in accordance with the printhead requirements. With the right temperature settings the “in” and “out” pressures are set in the range which prevents the printhead from dripping or sucking in air. The resulting flow rates are in a range of 10 to 200 ml/min depending on the printhead and have to be measured and maintained. At this point, the jetting performance can be analysed using a dropwatcher. The “in”/”out” pressures can now be adjusted with each jetting trial to find the region within which we achieve the best jetting performance. A flow rate that becomes too low can cause jetting instability and a delay/complete loss of nozzle recovery. A flow rate that is too high can affect the jetting straightness. The next parameter to test is the temperature. Temperature changes during the operation of a system should not fluctuate more than ±1°C. Any changes in temperature during jetting can affect drop size, jetting speed,as and jetting stability. As with pressure, temperature should be adjusted between jetting tests under the dropwatcher in increments of 0.5°C, while keeping other parameters constant. This should also produce a profile showing the ideal range in jetting performance, this time, relative to temperature. If the ideal temperature is different to the temperature set at the start of the procedure, the pressure range test can be repeated to see if the optimal pressure range changes with the new temperature value. Both pressure and temperature range tests would need to be repeated until the optimal pressure and temperature ranges stay constant. This entire procedure has to be repeated for each different ink chemistry, though it is a more complex procedure to swap out a printhead to test with the same ink. It is recommended to select as few printheads as early as possible in the development stages of a printing solution to avoid uneconomically lengthy development times. Functional fluids often have a high amount of solids in their chemistry and as such require frequent/constant agitation to prevent sedimentation, mentioned earlier. For chemists, it’s a challenge to design such fluids within the low viscosity requirements of piezo printheads, somewhere between 4 to 20 mPa s. Testing is recommended to avoid unpleasant surprises in the form of damaged printheads. Other parameters such as head voltage and waveform can also be analysed, however, they are outside of the scope of this article. A dedicated apparatus for complex inkjet development is the INKATRONIC Test Bench, with Dropwatcher shown in Figure, 6 below. With such equipment it is possible to gain productivity and have all the necessary tools at your side to effectively achieve your targets. Figure 6 - Shows the INKATRONIC Test Bench which includes a Meteor dropwatcher for analysing ink jetting in microscopic detail as well as a vacuum table for test prints. Join us at TechBlick's Future of Electronics RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped.For your special attendee discounts please contact us at mb@inkatronic.com.

Surface Lighting has the ability to change the world of design and change how we interact with products around us. It is a game changer for the printed electronics industry, since light and visual interfaces are becoming a part of any product. We are becoming completely depended on light as a indicator and design element, that communicates ambience, emotions, and statuses. Today Visual Interfaces have to be assembled through the hybrid electronics approach. LEDs are picked and placed and covered with light guides to achieve the target shape and form. Technologies like this maybe cheap to manufacture in mass, but they are hard to setup and to incorporate and any adjustment in shape requires additional setup costs and time. Surface lighting is paper-thin and thus has no space requirements. Affordable Surface Lighting technologies so far have been also accompanied with draw-backs of complex driving electronics, large size or lack of brightness. A technology that can meet all of this is OLED. OLED are made in process that are similar to the chip manufacturing industry. This makes them expensive in unit cost and even more in setup. Thus the dream of Light Everywhere, OLED Everywhere vanishes quickly on hard economical reality. Inuru has simplified the way OLEDs are manufactured by not taking the material into vacuum to to evaporate them, but taking the molecules and printing them. We are utilizing state of the art ink-jet technology used for color printing today. The infrastructure we use for an output of 8M panels require a fracture of the space than conventional evaporation processes. The additive manufacturing of ink-jet allows us to save materials, reduce cost and print any shape in real time, on demand like color. We are 3D printing lighting on a nano-meter precision. This technology will revolutionize the electronics manufacturing and will open printed electronics industry to a wider audience. SAVE THE DATE

Author: Jesus Zozaya | CEO of Voltera | jesus@voltera.io Goal: Design and print a high-performance ultra-high frequency (UHF) RFID tag using precision dispensing of nano copper ink on a paper substrate. Promising Technology: Radio Frequency Identification (known as RFID) is a technology that leverages wireless communication over radio waves to communicate with and locate objects. RFID tags are small label-like objects that are placed on an item which can be tracked and communicated with using an RFID reader — a handheld device that scans RFID-equipped items. UHF RFID tags are passive, meaning they don’t require a battery or power source. UHF RFID has many applications, being well-suited to use cases where non-contact data transfer and item localization can prove beneficial. For example, tracking inventory in a warehouse or manufacturing plant, acting as a high-speed point-of-sale scanner in consumer stores, enabling non-contact cashless payments, and even tracking donated blood bags in healthcare settings. While it seems like RFID tags are just fancy barcodes, they provide many benefits compared to traditional optical barcodes. RFID tags do not require a line-of-sight and are therefore resistant to bad lighting conditions and other environmental factors. You can quickly scan a room full of thousands of RFID tags without having to identify each individual tag (tags can even be scanned if they’re behind a wall!). RFID tags also integrate a user-writable memory space, enabling item identification, the ability to update information in the tag when it is scanned, and tracking the condition or state of the item. Perhaps most useful of all, RFID tags can be used to identify a location in a space, so a smart warehouse will always know where items are located in inventory. What’s the catch? Current RFID tag manufacturing methods, such as etched aluminum or screen-printed silver RFID tags require the use of hazardous chemicals and result in tags that are resistant to biodegradation and are not recyclable due to their laminate structure. With billions of RFID tags manufactured each year, this presents a substantial environmental impact. Join us at TechBlick's Future of Electroncis RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped Quantum Leap: A novel approach using printed nano copper inks on a paper substrate offers the potential of more cost effective, better performing, biodegradable RFID tags for the industry of tomorrow. The most common manufacturing method for RFID tags is etched aluminum, where powerful solvents are used to subtract material from an aluminum foil and PET laminate, creating the antenna pattern. As mentioned above, these chemicals are hazardous, the manufacturing process is water-intensive, and the produced RFID tags cannot be recycled or composted. Using nano copper inks in the same application enables the production of biodegradable RFID tags using an additive printing process. This means less material is used, there are no hazardous etchants, and less water is wasted. Providing equivalent electrical performance to the highest performing printed silver inks, these eco-friendly nano copper RFID tags also result in a significant cost reduction compared to both etched aluminum and printed silver RFID tags. Creating the RFID Tag We set out to create a high-performance RFID tag using our own custom antenna design, printed with Copprint’s LF-301 ink, an ink specifically formulated for use on paper substrates. Using Voltera NOVA’s high-speed prototyping capability, combined with industry-leading design software, we designed a tag in-house that could perform just as well, if not better than industry standard tags. Step 1: Design the Tag Using Autodesk Eagle™ we laid out the pattern for the antenna using the meander half-dipole antenna topology, commonly used in RFID. This design prioritizes all-around performance by emphasizing both near-field and far-field performance, while reducing space requirements and providing a lot of tuning possibilities. Once the preliminary design was complete, gerber files were exported for the next steps. Step 2: Simulate the Tag Since it can be challenging to properly characterize performance of an RF system, we first performed simulations of our design to determine its expected performance. Using MATLAB® Antenna Toolbox™, the preliminary antenna design was simulated and iterated upon. To obtain the desired performance characteristics including antenna sensitivity and directionality, the geometry of the antenna was fine-tuned. The finalized design had a minimum self-reflection coefficient (S11) of -29.42 dB at 922.50 MHz, passing the required maximum of -10 dB. This is also known as the resonant frequency where the tag will function best, which is well within the 902 MHz and 928 MHz frequency bandwidth for North American RFID tags. Step 3: Print the Tag After iterating, the design was finalized. We imported our files into NOVA’s software, then calibrated the Copprint LF-301 nano copper ink using NOVA’s integrated workflow to generate the appropriate ink settings. After experimenting with multiple nozzle geometries on the Smart Dispenser, best performance was obtained using a Nordson EFD 0.004” Optimum Chamfered Tip nozzle with a custom ink profile generated with NOVA’s calibration workflow. Once the ink was calibrated, a cardstock paper substrate was secured on the Vacuum Table Module. The design was then printed using NOVA, with each RFID tag taking less than 15 minutes to print. Step 4: Prepare the Tag After printing, we completed post-processing of the tag in order to properly unlock the potential of this ink. Copprint provided guidelines for this on their website. First, the RFID tag has to be dried in order to prepare it for further processing. It was placed in a blast dry oven for five minutes at 80°C. Next, the print must be sintered. Sintering is the process of chemically bonding the different microscopic sections of copper together to form one continuous conductor. This process is essential to unlock the full performance of nano copper inks. For Copprint, sintering was achieved by placing our print in our hot-press for 15 seconds at 270°C. Once this process is complete, we burnish the surface to prepare it for soldering. Step 5: Solder the Tag Upon completion of post-production, we attached the RFID controller IC to the antenna to complete the RFID tag. In production, a special adhesive known as anisotropic conductive adhesive (ACA) is often used to attach RFID IC’s to the antenna. However, since Copprint LF-301 behaves like copper, the IC could be soldered after sintering of the antenna was complete. Using solder paste and an air reflow station, the transceiver IC was bonded to the printed antenna. Results In the end, the RFID tag performance exceeded that of off-the-shelf RFID tags bought from market leaders. When tested side by side, we see the potential of nano copper ink RFID tags; while the commercial tags we acquired were made of a non-recyclable laminate, our RFID tag was composed simply of paper and copper ink, which made it compostable. In addition, our tag would be more cost effective to produce at scale. See how we made the RFID Tags Using NOVA enabled us to produce this RFID tag in-house with no upfront capital costs such as screen-printing screens. We only required the purchase of Copprint’s LF-301 ink. Additionally, by leveraging NOVA’s modular Smart Dispenser and built-in ink calibration workflow, we were able to get up and running with a new material very quickly. All of this resulted in a print time of 15 minutes per tag, enabling many design iterations each day rather than one iteration per week. Join us and the global community in Berlin on 17-18 OCT 2023 and let us together RESHAPE the Future of Electronics, making it Additive, Sustainable, Hybrid, Wearable, or 3D.

Authors Wim Christiaens | Quand Industries | Wim.Christiaens@quad-ind.com Textiles are tactile, sensorial and visual. Qualities can be modified or even expanded when technology is added, transforming passive textiles into active and interactive devices, monitoring and detecting bodily functions due to their constant contact with our skin. Printed electronics are also more durable than traditional electronics and can withstand multiple washing cycles, crinkling, friction and sweating. The lower production costs and easy scalability of printed electronics also stimulate the development of new (IoT) applications and a larger adoption of e-garments and smart fabrics in general, which can promote a healthier lifestyle and reduce the risk of disease, accidents and injuries in many industries. Their integration is straightforward. After printing the sensors on TPU they can be transferred onto the textile material via hot press lamination. Both are well-established techniques. Join us at TechBlick's Future of Electronics RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped. For special discounts on attendee passes please contact Wim.Christiaens@quad-ind.com Compared to traditional electronics manufacturing, printed electronics are easily scalable and low cost. They are durable, precise, efficient and comfortable to wear. They have excellent interconnectability. The PCB’s can be positioned in a remote spot, are small and don’t need much power to work. Applications that change our lifestyle Athletic monitoring: Train smarter, not harder A wide range of smart sportswear (e.g. shirts, insoles, sports bras) track vital signs (via printed ECG or EMG sensors), core temperature, and biomechanics both during training and in the recovery phase. It helps athletes to enhance performance, ensure a healthy athletic growth, help reduce stress and prevent different types of injuries. Alleviating the healthcare and medical sector Smart textiles serve as a functional and comfortable ‘wearable computer’ that help health care professionals by monitoring and communicating a patient's condition by detecting, storing, analysing, and transmitting physiological signals. Join us at TechBlick's Future of Electronics RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped. For special discounts on attendee passes please contact Wim.Christiaens@quad-ind.com Automotive and aerospace In the aerospace industry and in vehicle engineering, current applications focus on smart sensors integrated in interior fabrics and biometric monitoring for safety purposes. Information can provide insight into the driver's physical condition and level of fatigue, triggering haptic feedback through the steering wheel or warning alerts in the car's cockpit. Active workwear The monitoring of vital signs of workers in demanding environments and high-risk industries has been made easier. In regulated industries where safety rules restrict workers from wearing devices, smart workwear can give insightful information about the condition of workers or machine operators that can be used to optimize their well-being, performance and productivity. Thermal workwear to dynamically regulate body temperature of workers in cold climates is another huge application domain. Textile-integrated flexible heaters There is a steep rise of interest is heating technology for garments. Stretchable printed electronics heaters make it easy to incorporate heat into comfortable, elegant, flexible, lightweight clothing. The high precision that can be achieved with screen-printed circuitry also makes it simpler to provide warmth exactly where required and avoid areas of the body which don’t need any additional heat. Join us at TechBlick's Future of Electronics RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped. For special discounts on attendee passes please contact Wim.Christiaens@quad-ind.com

Stephan Harkema and Corné Rentrop | TNO at Holst Centre | stephan.harkema@tno.nl A growing desire for continuous data collection, real-time information, and connectivity has resulted in increased demand for electronic functionalities that are fully integrated in everyday objects. Consumer electronics, healthcare, wearable electronics, IoT, and smart packaging are examples of market segments that follow this trend. Printed circuit boards (PCBs) are state-of-the-art when it comes to creating electronic functions, but pose challenges with respect to sustainability. These highly integrated electronic products, where plastics, metals and semiconductor components are seamlessly combined, are a challenge to recycle. The only suitable end-of-life scenario is still limited to shredding and incineration. With increasing electrification, digitization, broad wireless integration (IoT) and welfare, the amount of waste from electronics and electronic devices increases drastically. An estimated 1.2 Mtons of Printed Circuit Boards (PCBs) end up in the total amount of annual e-waste[1]. Only a third is recycled in environmentally sound facilities. This means that around 800 million kilograms may be traded, recycled in a non-compliant and polluting manner or may end up on a landfill. There is a more eco-friendly alternative to PCBs: Hybrid and Printed Electronics (HPE). This technology is a big step forward compared to PCBs, but much more is needed to achieve circular production of next-generation electronics. Despite their name, printed circuit boards (PCBs) are not actually printed. They consist of multiple layers of electroplated copper on glass-fiber epoxy substrates onto which electrical components, so-called surface-mounted devices (SMDs) are assembled. The copper layers are etched with hazardous chemicals to create the circuitry. At end-of-life, the encapsulated copper and unrecyclable epoxy carrier make PCBs a recycling challenge. Transitioning from PCBs to HPE (Hybrid and Printed Electronicprovides immediate opportunities to achieve ecological benefits: reduced device thickness, lower weight, printed sensors, and additive instead of deductive manufacturing of the circuitry. Printed electronics is a disruptive technology that is on the verge of breakthrough in the automotive, lighting, and medical domains. Each use case represents a slimmer, lighter, more appealing, more practical, and less polluting alternative to the conventional device based on printed circuit boards (PCBs). However, in both types of electronics, PCBs, and HPE, the circuitry and SMDs contain potentially critical, high-impact metals embedded in plastics to protect them from external influences, such as mechanical damage and moisture. As opposed to PCBs, the environmental impact of HPE can be further reduced by using recyclable, bio-based, and renewable or compostable materials. Figure 1: roadmap to sustainable electronics Roadmap to sustainable printed electronics Most, if not all, products are mass produced. A first primary focus lies with a successful market entry which is often achieved by innovative functionalities in an aesthetic product design at competitive price levels. Manufacturing of such products is often not immediately optimized for low material usage, low power usage, and a minimal carbon footprint. Instead, single use and low recyclability are often accepted at this stage to achieve commercial success, which may be essential for the survival probability of the company. Petrochemical materials offer a high degree of reliability, low cost and supply security and are therefore ideally suited for high volume production in this first stage of the roadmap, as shown in Figure 1. A first step towards increasing a product’s sustainability is to address, and preferably extend, its end-of-life by enabling repairability, for instance by a modular design with repairable or replaceable components, or by enabling upgrades. Such steps do not immediately improve recyclability or reduce the environmental impact of production and the materials, but they do provide a significant improvement to the environmental impact by the simple fact that the product does not need to be replaced by a new one. Also energy consumption during the use phase may be addressed. For some examples, such as devices containing highpower elements (e.g. lighting), optimization of power usage may be an effective means of lowering the overall environmental impact. Join us at TechBlick's Future of Electronics RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped. For your spercial attendee discounts please contact us: stephan.harkema@tno.nl ] Following this second stage, a third step may be taken in which a product undergoes a simplification of its design with a reduction of coatings to limit material usage, production steps and overall energy consumption. Printed electronics technology offers an increasingly credible alternative to PCBs and perfectly matches this stage in the roadmap: 1) lower thickness, 2) printed functionalities instead of discrete SMD components that have a higher footprint, 3) recyclable thermoplastic polymers and 4) additive manufacturing as opposed to deductive etching of copper. Nonetheless, challenges still remain in terms of costs and reliability in comparison to the PCB. Circular use of materials, as depicted in the fourth stage in Figure 1, requires more drastic changes, especially to enable other choices at end-of-life. When end-of-life is reached, the product needs to be dismantled into its chemical building blocks. Here, printed electronics also provides opportunities, as many of the starting materials are meltable and therefore relatively easy to dismantle. The favoured cradle-to-cradle recycling approach is a possibility to further reduce the environmental impact. However, seamlessly integrated electronic products manufactured to survive rigorous testing in harsh environments cannot be disassembled so easily, which leaves shredding and incineration of these products as the only option at end-of-life. The plastics serve as energy carriers for metallurgic processes. While metallurgic processing at an industrial scale may be very efficient for metal recovery, the plastics are lost entirely. Recuperation of the plastics faces the challenge of achieving a high enough purity level to reach the material properties of the initial plastic. When combining plastics with coatings or metals or other plastics, purity levels plummet and only secondary use is realistic. Recycling of integrated electronics to yield metals, components and plastics separately and in a pure and circularly usable form therefore requires a method of disassembly prior to recycling. Not only does this allow circular use of all components and materials, it also enables higher recycling rates. It is therefore vital for electronics production in a circular economy to include design-for-recycling principles. In the before-last stage, bio-based materials may be introduced as a replacement for generally used fossil-based polymers. In the final stage, biodegradability is an option for specific use cases where disposal into the environment is likely or a more effective approach to recycling. Devices applied to the human body with a limited lifetime of days to weeks are well-suited to go this far in their sustainable developments, while others intended for long-term use are less likely to benefit from biodegradability. Materials from bio-based origins are considered to be environmentally friendly, but large volume production may put additional strain on food supplies and animal feed (1st generation feedstock) or land use for non-food biomass (2nd generation)[2]. Algae are a promising candidate for third-generation bio-mass due to a very high growth rate (5-10x terrestrial plants)[3]. Moreover, cultivation of algae do not strain food supplies and available cultivated farmland. Achievable lower environmental impacts Quantification of the environmental impact typically proceeds through a life-cycle assessment. Guidelines to achieve a lower environmental footprint for printed electronics were provided by Prenzel et al.[4]. Copper has a significantly lower global warming potential than silver, possibly up to a factor of 70[5]. While this choice for a different metal would lead to a more than 95% lower contribution to the GWP, it is limited to the printed circuitry alone, if processing remains otherwise identical. Similar values are possible for the plastic carrier if e.g. paper is a suitable alternative. However, reliability would then be at stake due to a high sensitivity to moisture/water, revealing the potential, but also the intricacies related to developing sustainable electronic products. At a higher integration level, ultra-thin organic photovoltaic solar cells were reported to demonstrate a 10-85% reduction in carbon footprint by a combination of a different substrate, less silver and a modified design[6]. For printed electronics devices closer to industrialisation, a recent life-cycle assessment by Tactotek indicated that, compared to PCBs, in-mould structural electronics (IMSE) enabled a reduction of the carbon footprint by 34-62%, depending on the application and its details[7]. The reductions in carbon footprint for these printed electronics examples are very hopeful and do not stand alone. More examples are available in the literature. Join us at TechBlick's Future of Electronics RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped. For your spercial attendee discounts please contact us: stephan.harkema@tno.nl ] Design-for-recycling (DfR) The benefits of the application of a design-for-recyclability would further enhance these values as a DfR enables the recovery of the materials. When comparing automated shredding and sorting of PCBs containing electronic waste to manual extraction of the PCB for recycling, higher recovery rates were obtained for the latter (95-99% vs 12-60%)[8]. Another study indicated that extensive dismantling and high-quality recycling would lead to the highest reduction of the product’s global warming potential[9]. Norgren et al. applied design-for-recycling to several use cases and examined the role of a DfR in a circular economy[10]. As described, design-for-recycling holds the potential to increase the quantity and value of materials recovered and reused from products that have reached their end-of-life. Important to realize is that improved recyclability provides a balance between reliability and recyclability: a part is typically designed to withstand rigorous testing (peel tests, pull-out tests, bending tests, stretching, ..), sometimes in combination with harsh environmental exposure (climate chamber set at elevated temperature and humidity, thermal shock tests, aging test at high T and/or with UV exposure). The specs and standards that must be met are often based on conventional PCB electronics and warrant re-evaluation of their applicability in a circular economy. The additional trade-off of recyclability versus costs may come in next, as additional measures or specialistic materials may be necessary to reach the DfR. The question is then when the gains in environmental impact exceed the potential loss in reliability and or potential increase in costs and which methods for quantification are accepted by the industry and policy makers. TNO at Holst Centre has developed a DfR approach that can be applied to various printed electronics devices, including in-mould structural electronics, flexible lighting, flexible sensors, and (medical) health patches. In this design, the encapsulant of the printed electronics and discrete semiconductor components can be removed at end-of-life. First demonstrations of the principles on in-mould structural electronics (IMSE) in the EU Treasure project led to successful device disassembly[11]. Upon removal of the polycarbonate encapsulant, that had been applied by injection moulding to a polycarbonate substrate with printed silver circuitry, the printed silver circuitry was exposed. Subsequent hydro-metallurgic processes by Treasure partner Univaq (University of L’Aquila) could target the printed silver directly and specifically without the need to chemically remove the PC beforehand[12]. A full life-cycle assessment, including the comparison of a recycling end-of-life scenario compared to shredding and incineration, is underway. Figure 2: schematic representation of a design-for-recycling with a) an electronic device encapsulated in plastic, b) first stage of dismantling with the removal of the plastic encapsulant, c) & d) second stage of dismantling that targets SMDs and (printed) circuitry and e) plastic substrate with any leftover (graphic) layers. Figure courtesy of Amires. Figure 3: a) forced mechanical disassembly of an IMSE device without DfR leading to rupture of the substrate, b) disassembly of an IMSE device with DfR; c,d) Flexible lighting device with DfR in on-state and off-state during peel tests Join us at TechBlick's Future of Electronics RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped. For your spercial attendee discounts please contact us: stephan.harkema@tno.nl ] Acknowledgements Holst Centre is a research and innovation partner specialized in health technologies, flexible and wireless electronics, powered by the shared expertise of imec and TNO. This research has been funded by the Dutch Ministry of Economic Affairs, and the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101003587 (EU Treasure project), No 101070167 (EU Ecotron project). Original electrical and injection-mould design were realized in the Flexlines project that received funding from Interreg Vlaanderen-Nederland. The authors would like to gratefully acknowledge the exceptional contributions from Peter Rensing, Pit Teunissen, Jan van Delft, Jeroen Schram, Gerwin Kircher, Adri van der Waal and dr. Margreet de Kok from TNO at Holst Centre, and Sanne Domensino and Joris Vermeijlen from Fontys University of Applied Sciences. We also gratefully acknowledge the wonderful support provided by Rick Leuven and Yibo Su from Brightlands Material Center for injection moulding with the Flexlines mould. References: [1] Baldé, C.P., D’Angelo, E., Luda, V., Deubzer, O., and Keuhr, R. Global Transboundary E-waste Flows Monitor – 2022, United Nations Institute for Training and Research (2022) [2] Coma M., Martinez-Hernandez E., Abeln, F., Raikova, S., Donnelly, J., Arnot, T.C., Allen, M.J., Hong, D.D., Chuck, C.J.Faraday Discuss., 202, 175 (2017) [3] Maliha A., Abu-Hijleh, B., Energy Systems (2022) doi:10.1007/s12667-022-00514-7 [4] Prenzel T.M., Gehring, F., Fuhs, F., Albrecht, S. Matériaux & Techniques 109, 506 (2021) doi: doi.org/10.1051/mattech/2022016 [5] Nuss P, Eckelman MJ (2014) PLoS ONE 9(7): e101298. doi:10.1371/journal.pone.0101298 (2014) [6] Välimäki, M.K., Sokka, L.I., Peltola, H.B. Int J Adv Manuf Technol 111, 325–339 (2020). doi:10.1007/s00170-020-06029-8 [7] Tactotek webinar “Environmental Performance of IMSE®”, 2022, https://www.tactotek.com/resources/webinar-environmentalperformance-of-imse [8] Ardente F., Mathieux, F., Recchioni, M. Resources, Conservation and Recycling 92, 158-171 (2014) doi:10.1016/j.resconrec.2014.09.005 [9] Alston, S., Arnold, J. Environ. Sci. Technol. 45, 21, 9386–9392 (2011) doi:10.1021/es2016654 [10] Norgren A., Carpenter A., Heath, G. Journal of Sustainable Metallurgy 6:761–774 (2020). doi: 10.1007/s40831-020-00313-3 [11] Harkema, S., Rensing, P., Domensino S., Verweijlen J., Godoi-Bizarro, D. submitted for publication [12] Ippolito, N.M.*, Romano, P., Passadoro, M., Pellei, G., Vegliò, F. Treasure Project H2020 - Recycling of automotive waste for the recovery of precious and critical metals: pilot plant tests. The 16th International Conference on Chemical and Process Engineering, Naples, May 21-24, 2023

Authors: Steliyan Vasilev1, Melanie Hoerr1, Michaela Kasdorf1, Sven Boehmer2 13E Smart Solutions, Krefeld, Germany 2ZSK Stickmaschinen GmbH, Krefeld, Germany steliyan@3esmartsolutions.de 1. Introduction Embroidery was historically a means of adorning fabrics with intricate patterns, a testament to human skill. However, in the modern era, this ancient art form has significantly evolved. In recent years, embroidery has undergone a profound transformation, emerging as a pioneering technology at the intersection of artistry and functionality. This article delves into the possibilities which embroidery offers for the production of Smart and E-Textiles, exploring technical intricacies, advantages, and challenges related to embroidered conductive traces. Join us at TechBlick's Future of Electroncis RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped. Contact us [steliyan@3esmartsolutions.de ] for a special attendee discount 2. Solutions for the E-Textiles Production Made Possible by Embroidery E-Textiles represent a fascinating synergy between traditional textiles and modern technology, serving diverse sectors like automotive, aerospace, sports and fitness, medical, home textiles, and wearable technology. Thanks to the exceptional precision and high degree of automation of embroidery technology, it is ideal for integrating functional elements into textiles, such as sensors, actuators, antennas, or electrodes. By use of conductive threads and specialized attachments for automated integration of electronic components, embroidery techniques, originally developed for aesthetic purposes, now enable reliable and scalable E-Textiles production. Embroidery makes possible the following innovative solutions, among all: Integrating and Interfacing Electrical Components and PCBs Semi-Automated Integration In decorative embroidery, the Appliqué technique is utilized to attach pre-made textile patches to the carrier fabric. This same method can be used for semi-automatic placement of printed circuit boards (PCBs). After the manual placement and adjustment of the PCB, the embroidery machine takes over, automatically fixing it to the fabric and establishing the electrical connections at the interface pads. Automated Integration Embroidery machines equipped with automated Sequin Placement Devices can be configured to incorporate functional sequins into textiles (Fig. 1a). Functional sequins can be equipped with SMD soldered components, such as LEDs or RFID chips. For larger circuit boards, whether rigid or flexible, embroidery machines fitted with automated PCB Placement Devices can precisely position and secure the PCBs to the textile (Fig. 1b), followed by embroidery of the electrical connections. Automated integration is especially valuable for achieving reliability and reproducibility in the production of E-Textiles on a large scale. Figure 1 Automated integration of functional LED sequins (a) and PCBs (b) by using automated Sequin Placement Device and PCB Placement Device from ZSK Stickmaschinen GmbH Embroidery of Complete Electrical Circuits By embroidering conductive traces onto fabric, placed PCBs and peripheral components can be electrically connected to each other, as well as to power sources or external circuitry. This approach allows for the automated integration of complete electrical circuits into textiles during a single production step. Integration of Conductive Fibers and Wires Tailored Wire Placement (TWP) and Tailored Fiber Placement (TFP) techniques allow precise conductor placement for applications such as illumination, textile-based heating, RFID antennas, and more. Embroidery of Conductive Areas With conductive threads, conductive areas in various shapes and sizes can be embroidered. These areas can serve a multitude of functions, including wide conductive traces, sensors, electrodes, and antennas, expanding applications from automotive control elements to advanced medical devices. 3. Advantages of Embroidered Conductive Traces Embroidery of conductive traces has opened up new horizons for Smart and E-Textiles, driven by several distinct advantages: Versatility in Design and High Precision Embroidery offers unparalleled versatility in design. Complex patterns and intricate geometries become feasible, catering to diverse application needs. The precision achieved in embroidery ensures that these designs are replicated accurately and consistently. Flexibility and Breathability One of the standout features of embroidered conductive traces is their inherent flexibility. They easily integrate with the carrier fabric, preserving its natural drape. Unlike printed circuits, embroidered traces allow textiles to breathe, enhancing wearability in clothing and comfort in various applications. Durability and Washability Embroidered conductive traces exhibit impressive durability. They withstand the rigors of daily use and multiple washing cycles, remaining fully functional over extended periods. This longevity contributes to the reliability and sustainability of embroidered E-Textiles products. Enabling Direct Connection to Electrical Components and PCBs Embroidery facilitates the direct integration of conductive traces with electrical components and printed circuit boards (PCBs). This approach eliminates the need for additional connectors or complex wiring, enhancing the product’s reliability and comfort and reducing production costs. 4. Challenges and State-of-the-Art Solutions for Embroidered Conductive Traces While there are clear advantages to using embroidered conductive traces, there are also associated challenges. In the following sections, we will outline the primary challenges and present state-of-the-art solutions to address them. a) Compensation for High Yarn Resistivity One of the main challenges in utilizing conductive embroidery threads is their intrinsic high resistivity of up to a few hundred Ohms per meter. To address this challenge, several state-of-the-art solutions have emerged: Multiple Passes and Use of Conductive Bobbin Thread A method to compensate for the high resistivity of the conductive thread is to embroider multiple passes using the so-called running stitch. Each pass adds to the overall conductivity, effectively acting like parallel resistors (Fig. 2a). Additionally, incorporating a conductive bobbin thread enhances conductivity by further reinforcing the electrical path (Fig. 2b). As an additional benefit, multiple embroidered passes compensate for the inhomogeneity in resistance throughout yarn length due to local damages in a single yarn pass during use, increasing the reliability of the E-Textiles product. Figure 2 Equivalent circuit of embroidered conductive trace with one, two, and three passes (a), and conductive embroidery (yellow) and bobbin (green) thread (b) Conductive Traces Embroidered as Filled Areas An alternative approach for reducing resistivity is to embroider conductive traces as filled areas, using the fill stitch rather than the running stitch. The high density of stitches in the filled areas enhances the overall trace conductivity. To ensure sufficient electrical contact between the stitches along the stitch direction, an underlayer must be added beneath the fill stitch, angled to the primary stitch direction (Fig. 3) [1]. Figure 3 Embroidered area with fill stitch without (a) and with a grid underlayer (b) b) Avoiding Conductive Thread Damage during Embroidery During embroidery, stitching directly into the conductive yarn can damage it, compromising electrical properties. Therefore, special attention must be given to the digitizing of the embroidery design to avoid placing stitches over previously embroidered threads as well as repetitive stitching in the same spot. To mitigate this while embroidering multiple running stitch passes, a swing factor can be introduced in the digitizing program, altering the stitching path slightly with each pass. This minimizes localized stress on the yarn, preserving its integrity and conductivity. Fig. 4 illustrates a conductive trace with four passes and an added swing factor, shown as a visualization in the embroidery machine’s programming software (a) along with a photograph of the embroidered trace (b). Figure 4 Conductive trace with four passes for increased conductivity and added swing factor, shown in the digitizing software (a) and after embroidery (b). When adding a swing factor, corners pose a specific challenge, leading to repeated puncturing at the same location (Fig. 5a). Rounding corners in the embroidery design is essential, as it significantly reduces the risk of stitching into the yarn, maintaining its electrical properties (Fig. 5b) [1]. Figure 5 Running stitch with three passes and an added swing factor, with multiple punctures in sharp edges (a) and without multiple punctures in rounded corners (b) c) Enabling Crossing and Insulation of Conductive Traces Complex E-Textiles designs often require multiple closely adjacent or intersecting conductive traces. Without proper insulation, unwanted electrical connections can occur when these traces come into contact. Adding non-conductive bridges between traces prevents unintended short circuits and maintains the desired electrical paths. Insulating bridges can be created by embroidering multiple layers of satin stitch with non-conductive thread, as depicted in Fig. 6a. It is crucial to ensure that the stitch directions of the bridge layers are angled in relation to the intersecting conductive traces. Covering conductive traces with non-conductive thread can also be used for insulation towards the surrounding environment. Fig. 6b illustrates an example of covered conductive traces connected to moss-embroidered electrodes for body signal acquisition. The covering prevents direct contact with the skin outside the electrode areas. For applications requiring waterproofing of the conductive traces, seam sealer in the form of tape or liquid, or dispensed polymer coatings can be utilized. Figure 6 Covering conductive traces with non-conductive thread to create insulating bridges between intersecting traces (a) and as a method of insulation towards the surrounding environment (b). 5. Conclusion The integration of conductive traces into textiles through embroidery offers a promising avenue for the development of Smart and E-Textiles. While the advantages of embroidered conductive traces make them a compelling choice for a wide range of applications, there are technical hurdles. Fortunately, various state-of-the-art solutions have been developed to address these challenges, ensuring that embroidered conductive traces can meet the demands of diverse applications. As technology advances and the demand for Smart Textiles grows, continued research and innovation in the field of technical embroidery will be essential. With ongoing efforts to refine techniques and materials, we can expect to see even more sophisticated and reliable embroidered E-Textiles, opening up new possibilities in wearable technology, healthcare, fashion, and beyond. References [1] McCann, J., & Bryson, D. (2023). Smart Clothes and Wearable Technology, Second Edition. Elsevier. Join us at TechBlick's Future of Electronics RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped Contact us [steliyan@3esmartsolutions.de ] for a special attendee discount

Kyosuke Michigami | Panasonic Industry Co., Ltd. [michigami.kyosuke@jp.panasonic.com ] Introduction Flexible printed circuit boards (FPCs) have found uses in a wide variety of applications, including health/wellness, mobile devices, aerospace and many more. Conventional FPCs consist of copper patterns formed on the surface of a flexible film using standard subtractive printed circuit board fabrication processes. Historically, polyimide resin (PI) has been widely used because it is readily available and possesses heat-resistant properties which make it compatible with high-volume assembly processes like solder reflow. However, new applications and device designs like wearables are driving the development of more conformable circuits. Stiff, high-modulus films such as polyimide are not suitable for these products. Currently available pliable, low modulus films like thermoplastic polyurethane (TPU) are not compatible with conventional surface mount (SMT) assembly processes. Researchers at Panasonic Electronic Materials are developing a new material technology that overcomes the limitations of these conventional FPCs. Fig1. Comparison of existing FPC materials (polyimide and TPU) and a target ULTRA pliable circuit board Join us at TechBlick's Future of Electroncis RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped . For special attendee discounts please contact us [[michigami.kyosuke@jp.panasonic.com] Development of Copper Clad Stretch (CCS) To address the limitations imposed by (1) the stiffness of polyimide and (2) the poor heat durability of TPU, the researchers developed an innovative approach using a copper-clad pliable and stretchable thermosetting resin. This construction is abbreviated CCS for Copper Clad Stretch technology; meaning it can be stretched, unlike conventional copper clad laminates (CCLs). The same resin system is used for both the circuitry layer and the insulative coverlay. The coverlay construction consists of a PET protective film, uncured resin, and polyimide release liner. The unique thermosetting polymer technology can be used in both fully-cured and un-cured format depending on the application. The polyimide release liner in the coverlay also acts as a mechanical support for the soft circuit board during SMT process discussed later in the paper. Fig2. Product portfolio achieved with thermosetting polymer technology Heat Durability Assuming exposure to typical SAC (Tin-Silver-Copper alloy) reflow conditions in the SMT process, the researchers conducted a solder float test at 288°C for 10 seconds and confirmed that no blistering or delamination of the CCS occurred (Fig.3). And the bare film made by etching CCS showed pliability and stretchability even after the solder float. On the other hand, TPU which is a thermoplastic resin, melted almost instantaneously and turned out to be incompatible with this SMT process. Fig3. Heat durability test (solder float) Mechanical Properties The resin of CCS is much more pliable than polyimide, leading to accommodation of various device form factors such as twisting and bending (Fig.4). Therefore, it is well-suited for non-planar and dynamic applications in healthcare, wearables, and the like. Fig4. Various form factors achieved with CCS resin A 10%-stretch cycle test for 10,000 cycles was conducted using a serpentine-patterned CCS (Fig.5). The sample finished the test without any failures in copper pattern. That means CCS has durability for stretch and is suitable for application requiring movements. Fig5. Stretch cycle test of serpentine patterned CCS CCS Compatibility with Standard FPC Fabrication Processes CCS was evaluated for standard PCB double-sided processes compatibility which consist of mechanical drilling, wet desmear, plating, chemical etching, coverlay patterning-molding, and surface mounting technology (SMT). The CCS could pass through the process. The polyimide release liner in the coverlay acted as a support structure for avoiding deformation during SMT. Fig6. Circuit fabrication process Conclusion This new CCS technology exhibits pliability and stretchability not possible with polyimide FPC products. Because of the temperature-resistant thermosetting resin system, CCS is compatible with reflow in the SMT process that TPU cannot withstand. As a result, CCS can be a foundational technology for building more pliable, conformable, and even stretchable devices utilizing conventional FPC manufacturing processes. As a use case of CCS, a reconfigurable intelligent surface (RIS) has been developed by researchers in Osaka University to effectively deliver the radio waves in 6G band (Fig.7, Ref.1). The radio waves at these frequencies are easily blocked by buildings and other physical structures. Researchers in Osaka University fabricated a metasurface reflector that can be attached to various locations and whose angle can be adjusted by expanding and contracting. By the combining a metasurface pattern and the inherent stretchability of CCS, it is possible to reflect radio waves efficiently. Fig7. Reconfigurable anomalous reflector fabricated on a stretchable elastic substrate. (a) Photograph of a prototype. (b) Schematic of a dynamic control of the reflection direction. (c) Photograph of a stretched sample mounted on a fixture. (d) Photographs of the sample before and after a stretch In addition to the research noted above, there are many product development projects in progress using the CCS technology. Panasonic Industry is proceeding with the development of CCS technology together with our customers and preparing for mass production. Join us at TechBlick's Future of Electroncis RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped . For special attendee discounts please contact us [[michigami.kyosuke@jp.panasonic.com] About us Panasonic Industry Co., Ltd. Electronic Materials Business Division Leading-Edge Materials for Circuit Boards, IC Packaging and Printed Electronics Panasonic Electronic Materials provides high-performance polymer-based products for Printed Circuit Board fabrication and Semiconductor packaging with industry-recognized brands like MEGTRON, Felios, Hiper and ECOM. These products are widely used in networking, automotive, aerospace, mobile, industrial, and other sectors where quality, reliability, and performance are paramount. Based on our core competency with thermosetting polymer chemistry, Panasonic research engineers in Osaka, Japan are developing a suite of game-changing new materials branded as BEYOLEX for printed electronics and related applications. We are working with OEM customers, research consortia, universities, and industry partners world-wide to bring these technologies to market. For quesitons please contact: Kyosuke Michigami | Panasonic Industry Co., Ltd. [michigami.kyosuke@jp.panasonic.com ] [Ref.1] Reconfigurable anomalous reflectors with stretchable elastic substrates at 140 GHz band Kato, Y.; Yonemura, K.; Seki, K.; Kambara, R.; Sanada, A. Nanophotonics, 2022, 12(13) https://doi.org/10.1515/nanoph-2022-0758 Join us at TechBlick's Future of Electroncis RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped . For special attendee discounts please contact us [[michigami.kyosuke@jp.panasonic.com]

Authors: Kai Keller and Lina März Introduction There are three big topics that shape the production environment of today and tomorrow: digitalization, additive manufacturing, and preserving natural resources/zero waste. Very tightly timed supply chains and globally distributed and connected production processes are already real and only possible because of digitalization. Additive manufacturing knocks on the door of many industrial areas, such as automotive and aerospace. Preserving natural resources and zero waste will become standard in many areas and will be the financially most convenient opportunity. Printed circuit boards (PCBs) are manufactured mainly in Asia but distributed just-in-time all over the world. In our laptops, cars, trains, planes, TV's, audio systems, mobile phones, we all use dozens of them every day, without even realizing it. The recent stress that has been put on these supply chains also lead to investments into new facilities in North America, Europe, as well as South East Asia. So many decision makers in electronics manufacturing are currently concerned with the question which technologies they are going to use for the newly built facilities.[ See for example SEL’s story in PCB007 Magazine, Vol. 13, Number 8, August 2023, https://pcb.iconnect007.com/ ] Today, the production process for PCBs is mainly subtractive, indicating that lots of expensive resources are wasted, are not reused, and eventually increase the costs. This means PCB manufacturing is at home in a global, digital world but will eventually suffer from subtractive processing, waste of resources, and more complex applications and layouts. Inkjet printing by nature is a digital technology, from image processing to discrete droplet deposition. It is also an additive manufacturing technology. Expensive materials are only deposited where they are needed, and even the amount of material can be adjusted locally. Three dimensional structures are possible without any extra effort. This indicates that inkjet printing is preserving resources and minimizing waste. This article will describe the process of applying a solder mask layer by means of inkjet printing in the PCB production. It will briefly describe a PCB and outline the benefits that inkjet printing brings. This will be followed by a detailed description of the steps that were necessary to establish a stable industrial process. Join us at TechBlick's Future of Electronics RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped. Contact us for your special attendee discount [Authors: Kai Keller ] Why Inkjet Printing for Deposition of Solder Mask on PCB's? Typically, a uniform solder mask layer is deposited by a coating technology such as curtain coating or screen printing. Also, dry films are available. All have in common that they cover the whole board. After a drying step, the design is transferred onto the board via a photo mask. For each design, an own photo mask needs to be created. Alternatively, direct imaging processes with a laser are used. After illumination, the dried film is developed, and the unwanted areas are stripped and washed away. A final curing step is performed in order to achieve the full functionality. Typically, this consists of a so-called UV bump and thermal curing in a belt oven. By summing up all the equipment needed, it's no wonder that a single production line can easily be dozens of meters long and requires a lot of staff with different skills. The inkjet technology in contrast locally deposits the UV-sensitive material and pins it in-situ with an LED lamp. The image is loaded digitally and can be changed after each board and even be adjusted to each board individually. It is saved digitally and does not use any footprint. After the same final cure from the conventional process, the board is finished. This indicates that PCB manufacturers can drastically reduce the amount of production steps that translates in less investment cost and space for machinery and less consumption of electricity and consumables and therefore a very fast return on investment. Figure 1 shows the process flows of the conventional and the inkjet process. Besides, these economic and environmental aspects inkjet exclusively opens the door to a unique combination of other features that gives the PCB production industry a new level of freedom. This allows the industry to be prepared for new applications such as high frequency and 5G. Figure 2 shows an inkjet-printed solder mask on a PCB and gives an overview of some unique features. In contrast to the conventional deposition technologies, where the layer thickness is the same over the whole board, with inkjet printing, the thickness can be adjusted locally without any extra effort. There are a lot of reasons why this is beneficial for the PCB manufacturing process. Let us name three: - Thickness zero, i.e., no solder mask where it is not required, in order to safe material or increase process stability. - A locally adapted thickness to ease subsequent SMD assembly. - Higher thickness at conductor or pad edges to reach higher break-through voltages. In summary, the main advantages are as follows: Digital production technology Additive manufacturing allows for locally adjustable thickness of layers New features are possible Labeling functions come for free Up to 80% less ink, as it is only print where required Higher yield Reduced space Reduced energy consumption Very fast return on investment What Are the Requirements and What Makes Inkjet Printing of Solder Mask Tricky? The requirements of the solder mask are defined in several norms, mainly by the IPC – Association Connecting Electronics Industries. IPC originated from the Institute for Printed Circuits. We will now describe some challenges that one faces when depositing a solder mask onto a PCB by means of inkjet printing. First of all, the solder mask ink itself is a sophisticated material. Actually, one has to develop two materials. As an ink, it needs to have a very low viscosity, must be a Newtonian fluid, and must allow for perfect jetting in the tiny nozzles. After curing, the material needs to be extremely stable to mechanical impact and withstand harsh temperature cycles (-30 °C to +170 °C) and strong chemicals, e.g., during Ni-Au plating. Another point is the surface. A board when it just arrives to the solder mask deposition consists of two different surfaces: the glass fiber compound (FR4) and the copper (Cu). Unfortunately, the surface energy of these areas largely differ. While the ink stays quite well on FR4, it spreads tremendously on Cu. In addition, the height difference between FR4 and Cu can be more than 200 μm. This can have a large impact on the deposition accuracy. Every PCB job is different. This indicates that PCBs can vary in size and thickness. Because of previous production processes, they can have bows and warpages and because of the still often manual handling even kinks. As if this was not enough, PCBs have many holes of different radii ranging from 0.1 mm up to 5 mm, of course randomly distributed over the whole area. Still, for a good performance, often absolute drop placement accuracies in the range of ± 20 μm are required. This calls for highest demands in the substrate table design and the jetting performance. The requirements and properties of the solder resist and the printed solder resist layer are anchored in IPC-SM-840. Properties can be verified using selected test methods. The test procedure and instructions for carrying it out can be found in the test manual IPC-TM-650. Typically, the properties are divided there into visual, physical, electrical, mechanical, and chemical properties/requirements. Join us at TechBlick's Future of Electronics RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped. Contact us for your special attendee discount [Authors: Kai Keller ] How to Get to Inkjet Printed PCB's To realize the application of inkjet printing, the solder mask onto PCB's different aspects have to be taken into account, such as the choice of ink and printheads, the process development, and the machine design. Figure 3 gives an overview of typical factors that define the process and printing machine. Although the overview is generic, most of the items are relevant for the inkjet solder mask process. The process development of each application follows the following route: Printhead selection Ink selection & material compatibility Waveform development Print process implementation System development (optional) On-site process support It is a common misconception, especially in time critical projects, to take the second or third step before the first. Maybe it is possible to produce a nice appearing PCB for a proof of concept, but in production, stability and more importantly predictability are crucial. Solid results based on systematic and repeatable tests are helping to identify the process window, maximize customer satisfaction, and to reduce costly field operations. Data Handling In the PCB industry, gerber is the dominating file format. Like in any other area, the conversion from vector data to discrete/digital images comes at the expense of truth to detail. Photoplotters and lasers both have this loss, but as they are operating in the range of several 10 000 of dpis, the artifacts are small. For inkjet printing, with feature sizes in the range of 30 to 80 μm and resolutions in a similar range, more care has to be taken for converting the print images. Figure 4 visualizes the challenge. The raster image processor has to make a discrete decision based on the vector layout and the printing resolution, whether it generates a printed dot or not. For low printing resolutions, this can lead to artifacts, such as visible steps and missing dots. A high resolution would increase the level of detail but would lead to an overflow of ink or increased thickness. We have developed a conversion algorithm that considers the vector file, the real drop diameter on the substrate, and the printing resolution and adjusts the droplets in such way that the maximal level of detail can be achieved without increasing the resolution and thus not compromising throughput. As mentioned before, conventional solder mask processes are subtractive, indicating that the full board is covered with ink and then structured. This indicates that the appearance and the geometry of inkjet-printed structures are by nature different. If one would now just use the conventional processing recipes, the result would be far from optimal. This is why, for inkjet, new design rules needed to be developed in close cooperation between technology providers, like Notion Systems and technology users, our partners, and clients. This ensures that the printed result looks more alike their conventional counterparts. Machine Concept At Notion Systems, we have developed a machine concept, that is shown in Figure 5 that can be used either in manual mode or be upgraded to operate fully automated with load and unload. Our print unit covers the full substrate width with up to 20 000 nozzles, each firing more than 20 000 tiny droplets per second. The vacuum table is designed in a way that it can hold different sizes of PCBs without any mechanical clamps. An integrated and automated non-contact cleaning system ensures that the printheads are always in good condition. The machine is easy to operate and is designed so that all important parts can be reached easily. Print Images Figures 6-10 show some examples of inkjet-printed solder masks structures. They highlight what is possible today. Summary and Outlook The solder mask on a PCB is perfectly suited for inkjet printing. The reduction of production steps decreases the cost and space requirements. Inkjet printing produces results that meet all requirements specified in the relevant norm for solder mask IPC 840. In addition, inkjet printing enables the implementation of useful and in its combination unique features, such as no mask in holes, locally adjusted thickness, or smart labeling. Yet, soldermask is not the end of the story, there are many more subtractive processes in electronics manufacturing that need a closer look and possibly a replacement, if one considers what is possible with additive processes in general and inkjet technology in particular, today. Questions? Please write to kai Keller and Lina März Join us at TechBlick's Future of Electronics RESHAPED conference & tradeshow in Berlin on 17-18 OCT 2023 - www.techblick.com/electronicsreshaped. Contact us for your special attendee discount [Authors: Kai Keller ]